Characterization of ferric reducing activity in roots of Fe‐deficient <i>Phaseolus vulgaris</i>

Bienfait, H. Frits; Bino, R.J.; Bliek, A.; Duivenvoorden, Joost F.; Fontaine, Jean-Gonzague

doi:10.1111/j.1399-3054.1983.tb00757.x

Cited by 205 publications

(100 citation statements)

References 23 publications

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“…These authors suggested that an "enzymic reduction of ferric ion on the plasmalemma of cortical cells of roots" was a key facet of iron assimilation by iron-deficient peanut plants [32]. Bienfait and colleagues [31,33], studying bean plants, reached similar conclusions concerning the involvement of an Fe3+-reducing enzyme in the cortex or epidermis cell plasmalemmas. In addition, data indicating the use of cytosolic NADPH as the electron source for Fe3+ reduction were also presented [33].…”

Section: Plant Iron Assimilation Modelssupporting

confidence: 51%

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Siderophores, the iron nutrition of plants, and nitrate reductase

Castignetti

John

1986

FEBS Letters

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Section: Plant Iron Assimilation Modelssupporting

confidence: 51%

“…The demonstration of Fe3+ reduction at the root surface [29,31] resulted in the proposal that a 'ferric ion reductase' is an intimate component of iron assimilation in plants.…”

Section: Plant Iron Assimilation Modelsmentioning

confidence: 99%

Siderophores, the iron nutrition of plants, and nitrate reductase

Castignetti

John

1986

FEBS Letters

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“…5). A broad range ofhigh Fe3" reducing ability, extending into the acid pH range, has been demonstrated for peanut roots (15) and bean roots (1). Reduction of rhizosphere pH is common under conditions of Fe deficiency for most nongraminaceous plant species (16).…”

Section: Ph Responsementioning

confidence: 99%

Dependency of Iron Reduction on Development of a Unique Root Morphology in Ficus benjamina L.

Rosenfield

Reed²,

Kent³

1991

Plant Physiol.

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The activity of the Fe3+ reductase of excised adventitious roots of Ficus benjamina L., grown in hydroponic culture without iron, was determined by a colorometric assay simplified by the use of a microplate reader. Reductase activity remained the same from pH 4.5 to 6.5 and decreased sharply above pH 6.5. Acetate buffer inhibited reduction. During early stages of root growth, excised roots did not exhibit Fe3 reductase activity. After several weeks and extensive root system development, Fe3+ reduction still was not detectable in primary roots, but intermediate and high rates of reduction occurred in lateral and newly formed root clusters, respectively. Clustered roots only developed on plants grown at O or very low (<1 micromolar) iron. Microscopic examination revealed the root cluster to be composed of up to 30 lateral roots, usually less than 1 millimeter in diameter and 1 centimeter in length, that were completely covered with root hairs.Rooted cuttings were washed free of sand, rinsed in 2.0'mM Na2EDTA to remove any adsorbed Fe, and then inserted into Styrofoam trays and floated on aerated modified Hoagland solution 1 (pH 6.3) without Fe, and containing 1 mM KH2PO4, 5 mM KNO3, 5 mM CA(NO3)2, 2 mM MgSO4, 11 uM MnSO4, 0.7 ,uM ZnSO4, 0.3 ALM CuSO4, 0.16 AM (NH4)6Mo7024, and 46 ,uM H3BO3. All materials coming into contact with plants or nutrient solutions were rinsed with 0.1 N HCI followed by 2.0 mm Na2EDTA to remove iron contamination. Nutrient solutions were changed weekly. The plants were grown under greenhouse conditions of 30°C day/25°C night (±5°C) and 45 to 85% RH.

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“…Since EDTA and BPDS complexes are membrane impermeable (Anderson and Morel 1980;1982;Price et al unpubl. ) (Bienfait et al 1983;Bienfait 1987), the ferric reductase lacks substrate specificity, as cells reduced Fe(III) bound to a variety of organic ligands (Table 4). Indeed, T. oceanica was able to reduce Fe bound to the fungal siderophore DFB at fast rates.…”

Section: Reduction Of Fe(iii) Bound To Dtpa and Dfb-mentioning

confidence: 99%

Nitrate regulation of Fe reduction and transport by Fe‐limited Thalassiosira oceanica

Maldonado

Price

2000

Limnology & Oceanography

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Under Fe-limiting conditions, nitrate (NO 3 Ϫ )-grown marine diatoms have higher intracellular Fe requirements, but divide as fast or faster than ammonium (NH 4 ϩ )-grown cells by maintaining faster steady-state Fe uptake rates. Here we report that Thalassiosira oceanica, clone 1003, possesses an Fe reductase that reduces Fe(III) bound to a variety of organic ligands, including the siderophore desferrioxamine B (DFB), a high affinity, Fe(III)-specific ligand. Reduction is mediated extracellularly and is induced by Fe deficiency. Cellular rates of Fe(III) reduction are significantly faster in NO 3 Ϫ -than in NH 4 ϩ -grown cultures suggesting a link with N metabolism. At subsaturating Fe concentrations, short-and long-term Fe uptake rates are also significantly faster in NO 3 Ϫ -than in NH 4 ϩ -grown cells. The results suggest that when Fe is limiting, faster rates of reduction of organically bound Fe(III) by phytoplankton promote faster rates of Fe transport and growth. The implications of these findings could be significant for understanding phytoplankton Fe nutrition in oceanic waters where organic complexation dominates the speciation of Fe. We hypothesize that the reductive Fe transport pathway may enable phytoplankton to directly utilize Fe bound to strong organic ligands in the sea.Iron plays a catalytic role in many biochemical reactions as a cofactor of enzymes and proteins involved in chlorophyll synthesis, detoxification of reactive oxygen species, respiratory and photosynthetic electron transport, and N assimilation. Changes in the activity of these reactions or their replacement by functionally equivalent Fe-deficient pathways can greatly influence cellular Fe requirements of organisms. Because the NO 3 Ϫ assimilatory pathway is highly Fe dependent, utilization of NO 3 Ϫ by marine centric diatoms (Thalassiosira spp.) imparts a higher metabolic demand for Fe than the use of NH 4 ϩ . The demand for Fe is such that the Fe quotas (Fe : C) of NO 3 Ϫ -grown cells are 1.8 times higher than those of phytoplankton using NH 4 ϩ (Maldonado and Price 1996). Despite the higher Fe requirement for NO 3 Ϫ assimilation, under moderately Fe-limiting conditions (ca. 0.7-0.85 / max ), growth rates of NO 3 Ϫ -amended cultures are not slower than those of NH 4 ϩ -amended ones (Maldonado and Price 1996). Nitrate-grown cells apparently compensate for their extra Fe requirement by sustaining faster steadystate Fe uptake rates (Maldonado and Price 1996). The 1 To whom correspondence should be addressed. Present address: 5741 Libby Hall, School of Marine Sciences, University of Maine, Orono, ME 04469 (maria.maldonado@maine.edu). AcknowledgmentsWe thank P. Tortell, C. Payne, Z. Chase, and J. Granger for valuable discussions, suggestions, and comments on earlier versions of this manuscript. The help of E. Maldonado-Pareja and C. Molony in the lab was particularly appreciated. We are grateful to M. Soon (U. of British Columbia) for CHN analysis, to W. King (Colby College, ME) for guidance with the Fe(II) chemiluminescence ...

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Characterization of ferric reducing activity in roots of Fe‐deficient Phaseolus vulgaris

Cited by 205 publications

References 23 publications

Siderophores, the iron nutrition of plants, and nitrate reductase

Siderophores, the iron nutrition of plants, and nitrate reductase

Dependency of Iron Reduction on Development of a Unique Root Morphology in Ficus benjamina L.

Nitrate regulation of Fe reduction and transport by Fe‐limited Thalassiosira oceanica

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